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Tungsten Filament bending and production

  1. Aug 17, 2010 #1
    Tungsten Filament bending and production!!

    my machine produces filaments for a UV lightbulb, the filaments are basically tungsten coiled tightly around a tungsten shank, and the machine used to do this perfectly! however it was switched off for a about a year during development.

    but now when it comes to engage the wire to coil up around the shank it more often than not splits the end of the tungsten wire and does not catch and wind up, can anyone think of any factors that may contribute to this happening?

    i think the wire used may be different, but have no idea what was used previously, and the programming seems sound (as it used to work)

    ive also used heat to make the tungsten more ductile as it is wound, this seems to help but it not enough.

    can pure tungsten have very differing properties that could make a machine work with one reel and not with another?

    any help would be very much appreciated!
  2. jcsd
  3. Aug 17, 2010 #2


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    Re: Tungsten Filament bending and production!!

    Attempting to troubleshoot a complex tool over the Internet! That is asking a lot. We have not been able to watch the machine operate or even seen the machine for that matter.

    My suggestion would be to watch it operate very closely. Figure out exactly what it is now doing. Could there be a part that is sticking? Machines that sit idle for long periods of time are difficult to get going again, perhaps some lubrication is needed.

    Good luck but I really cannot see how we can help you. At this point I would say, get up from the computer, go to your machine and watch it operate until you understand it thoroughly. If some part is sticking simply reptitious operation may finally free it up.
  4. Aug 17, 2010 #3


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    Re: Tungsten Filament bending and production!!

    I would expect that there is an equipment manual and procedure document to which one should refer. You should probably consult the manufacturer of the winding machine.

    Hopefully you're heating tungsten in an inert environment. Air will make it brittle when W interacts with O.

    Is it pure tungsten, or was it alloyed. Re makes it a bit more ductile, but also more expensive.

    One could consult with a tungsten supplier, e.g., the company from which one bought the wire.
  5. Aug 17, 2010 #4


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    Re: Tungsten Filament bending and production!!

    Yeah, pure tungsten would be extremely brittle.

    One might try calling GE's tungsten plant. Not sure of the number, but it's located on Tungsten Rd. in Euclid, Ohio, USA so you could probably google to find the phone number. Not sure if they would supply wire in small quantities, but it's worth a try.
  6. Aug 17, 2010 #5
    Re: Tungsten Filament bending and production!!

    I was going to point out that if the wire had been sitting for a year, it could have become more brittle. However, if you are playing with the wire, just about anything you do to tungsten can make it more brittle.

    The best thing to try is to get some fresh wire from the original supplier, perhaps with some advice. It sounds to me like you do NOT want to get in the business of drawing tungsten wire. A few companies have specialized in this for almost a century. Might as well let them do what they do well.
  7. Aug 17, 2010 #6


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    Re: Tungsten Filament bending and production!!

    If Mo, and I think W, get contaminated with Ni, they can also become brittle.

    H. C. Starck (Euclid, OH USA, maybe the former GE tungsten facility) and Plansee (http://www.plansee.com/wires.htm [Broken]) are two companies specializing in refractory alloys.
    Last edited by a moderator: May 4, 2017
  8. Aug 20, 2010 #7
    Re: Tungsten Filament bending and production!!

    thanks for the brainstorm, im a student but have been taken on part time to fix this thing and was in at the deep end! think ill have to get onto the suppliers, i know we're using plansee... the mashine was built in-house, its a prototype, but thanks for the help, i found that grinding it or getting very hot and cutting stops it splitting the wire, and am ordering some alloyed tungsten soon, but i dont know how it will react in the UV lamp, could it give a different spectrum of light if alloyed with Re or Thorium?
  9. Sep 11, 2010 #8
    Re: Tungsten Filament bending and production!!

    Reminding that W is An HCP structured metal
    and most HCP structures show brittleness

    so pure W will have a pronounced effect on such forming operations,
    as working at higher themperatures has not proved fruitful
    then alloying is the next option.
    It will be better to look for alloyed Tungsten ..
  10. Sep 12, 2010 #9
    Re: Tungsten Filament bending and production!!

    I worked with electrodes made of tungsten with 2% Thorium added. The purpose in adding the Thorium was so that alpha particles from the Th would reduce the work function at the surface. (Make it easier to establish an arc.) I have no idea how the Th affected the hardness, etc., one company made the wire, another wound it into electrodes, and so on.

    Rhenium should make the Tungsten harder, which is probably not what you want. If push really comes to shove, you could buy multi-stranded tungsten wire and run it through a tool to make it into one more flexible strand.

    We used to have a tool clamped to a workbench to do that. Choose the right two disks for the final diameter put the wire in and crank. (Actually, it was much easier to do two or three passes, even with copper wire.) I suspect today such a tool would be motor driven, spool to spool, but we only used it on the exposed ends of copper cables. (Why do it? For the cables involved, it increased the resistance very slightly, but eliminated cracking near the clamps. Net win for customers, the cables lasted longer, even if they still had to be replaced from time to time.)
  11. Oct 11, 2010 #10
    Re: Tungsten Filament bending and production!!

    Normally all additives which can be used in electrode wire for UV-lamps increase brittleness. Normally wire is pure Tungsten and very LITTLE heat, only around 40°C. Just put a very soft flame at the point where the bend begins.

    Good luck.
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